Computing the distributions of stress and strain in a body with the complex geometry, boundary conditions, and material properties of the heart is a difficult yet worthwhile endeavor. The most promising method for obtaining numerical solutions to this problem is the finite element method. In this chapter, we review the use of finite element analysis for modeling ventricular mechanics. And we conclude by presenting a new axisymmetric finite element model of the passive left ventricle with a realistic geometry and fibrous architecture, physiological boundary conditions, and a three-dimensional constitutive equation.
IntroductionThe distributions of stress in the ventricles of the heart are determined by (1) the three-dimensional geometry and fibrous architecture of the ventricular walls, (2) the boundary conditions imposed by the ventricular cavity and pericardial pressures and structures like the fibrous valve ring skeleton at the base of the ventricles, and (3) the three-dimensional mechanical properties of the myofibers and their collagen interconnections in the relaxed and actively contracting states. Many of these determining factors have been quantified in experimental studies, some of which are described in detail in this book.For example, Streeter and Hanna [72,73] and Nielsen and coworkers [56] have made detailed studies of the three-dimensional geometry and myocardial fiber architecture of the ventricles of the dog heart. Measurements of left and right ventricular pressures in patients are quite routine. And extensive data have been collected on the passive and active uniaxial material properties of isolated papillary muscles and trabeculae from various mammalian species [64,74]. Although fully triaxial material testing still presents significant technical difficulties, biaxial stress-strain testing of excised two-